Effects of Melatonin Supplementation on Insulin Levels and Insulin Resistance: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Antioxidant supplements relieve insulin resistance but do not improve lipid metabolism in women with polycystic ovary syndrome: a meta-analysis of randomized clinical trials

Objective: The effect of antioxidant supplements on glucose metabolism and lipid profiles in polycystic ovary syndrome (PCOS) remains controversial. This systematic review and meta-analysis aimed to evaluate whether antioxidant supplements improve glucose metabolism and lipid profiles in women with PCOS to provide optimal nutritional supplement advice in clinical practice. Methods: The search was conducted across multiple medical databases from inception to January 1, 2022 and performed following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. A random effects model was used to calculate the overall effects. Results: Eighteen trials (1113 participants) were included. Antioxidant supplements significantly improved insulin resistance (95% CI, -0.62, -0.30; p < 0.00001; I² =48%), fasting insulin (95% CI, -0.80, -0.44; p < 0.00001; I² = 48%), and fasting plasma glucose (95% CI, -0.54, -0.21; p < 0.00001; I² = 38%) in patients with PCOS. However, antioxidant supplements were found to not improve most indices of lipid profiles in PCOS except triglyceride. Conclusions: Antioxidant supplements are an effective intervention for relieving insulin resistance but do not significantly improve lipid metabolism in women with PCOS.

The Role of Melatonin in Chronic Kidney Disease and Its Associated Risk Factors: A New Tool in Our Arsenal?

BACKGROUND

The increasing incidence of chronic kidney disease (CKD), as a consequence of the high prevalence of arterial hypertension and type 2 diabetes mellitus (T2DM), warrants the need for developing effective treatment approaches. In this regard, the pineal gland-derived hormone melatonin may represent an appealing treatment approach of CKD and its associated risk factors.

SUMMARY

Targeting the adverse pathophysiology surrounding CKD and its associated risk factors has been the concept of pharmacologic treatment developed for its management. This review article aimed to present the role of melatonin in this direction, by providing an overview of melatonin's physiology followed by its effect as a therapeutic agent in arterial hypertension and T2DM.

KEY MESSAGES

Melatonin, the primary darkness hormone, possesses pleiotropic mechanisms of action which may have important implications in various pathologic states since its receptors are situated across various organ systems. As a treatment tool in arterial hypertension, melatonin may be efficacious in reducing both daytime and nocturnal blood pressure by influencing endothelial function, oxidative stress, the autonomic nervous system, and the renin-angiotensin system. Melatonin may also increase insulin sensitivity and β-cell function. However, late meal intake may be detrimental in glucose regulation, as consumption close to melatonin peak concentrations may induce hyperglycemia and insulin resistance. This finding may explain the inconsistent glycose regulation achieved with melatonin in clinical trials and meta-analyses. Additionally, the presence of genetic variants to melatonin receptor 2 may predispose to T2DM development. Finally, we present the available preclinical evidence supporting melatonin's efficacy in ameliorating CKD's pathophysiology since melatonin supplementation has not been adequately explored in patients with CKD. The combined use of stem cells with melatonin is an appealing therapeutic approach which ought to be assessed further.

Effects of exogenous melatonin supplementation on health outcomes: An umbrella review of meta-analyses based on randomized controlled trials

Various melatonin supplementations have been developed to improve health outcomes in various clinical conditions. Thus, we sought to evaluate and summarize the effect of melatonin treatments in clinical settings for health outcomes. We searched PubMed/Medline, Embase, and Cochrane Library from inception to 4 February 2021. We included meta-analyses of randomized controlled trials investigating the melatonin intervention for any health outcome. Based on the different effect sizes of each meta-analysis, we calculated random models' standardized mean differences or risk ratios. We observed robust evidence supported by statistical significance with non-considerable heterogeneity between studies for sleep-related problems, cancer, surgical patients, and pregnant women. Patients with sleep disorder, sleep onset latency (SMD 0.33, 95% CI: 0.10 - 0.56, P < 0.01) were significantly improved whereas no clear evidence was shown with sleep efficiency (1.10, 95% CI: -0.26 to 2.45). The first analgesic requirement time (SMD 5.81, 95% CI: 2.57-9.05, P < 0.001) of surgical patients was distinctly improved. Female patients under artificial reproductive technologies had significant increase in the top-quality embryos (SMD 0.53, 95% CI: 0.27 - 0.79, P < 0.001), but no statistically clear evidence was found in the live birth rate (SMD 1.20, 95% CI: 0.83 - 1.72). Survival at one year (RR 1.90, 95% CI: 1.28 - 2.83, P < 0.005) significantly increased with cancer patients. Research on melatonin interventions to treat clinical symptoms and sleep problems among diverse health conditions was identified and provided considerable evidence. Future well-designed randomized clinical trials of high quality and subgroup quantitative analyses are essential.